The Pacific Ocean is a hotbed of tectonic activity, hosting a vast majority of the world’s earthquakes and volcanoes. It even has the highest concentration of volcanoes anywhere in the world, with 1,133 in a space the size of New York state. Now, the Pacific gets to add another superlative to its geologic record book—the world’s largest volcano, Tamu Massif.

Probably the best view of Tamu Massif you and I will ever get.

Geologists and oceanographers have known about the seamount for some time. It’s one of three large underwater mountains that make up the Shatsky Rise, an underwater formation between Hawaii and Japan. What they didn’t know was that it’s a single volcano. Instead, scientists assumed it was a collection of magma vents that had spewed so much molten rock that they merged, appearing as one mountain. New data refutes that, though. The surveys were conducted in 2010 and 2012 and published yesterday in Nature Geoscience.

Alexandra Witze, writing for Nature News:

Sager and his colleagues were startled by findings they made after sailing the research vessel Marcus G. Langseth over Tamu in 2010 and 2012. They used air guns to send seismic waves through the mountain, and monitored the reflections. The seismic waves penetrated several kilometres into the massif — and showed that all of its lava flows dipped away from the volcano’s summit, implying a central magma vent. “From whatever angle you look at it, the lava flows appear to come from the centre of this thing,” says Sager.

Tamu Massif doesn’t poke it’s head above water like Mauna Loa—which previously held the title of “world’s largest volcano”—but what Tamu lacks in height, it makes up for in breadth. It covers an area on the seafloor comparable to the British Isles. Perhaps more notable, its footprint is about as large as Mars’s much taller Olympus Mons, which is still the solar system’s largest known volcano.